From mboxrd@z Thu Jan  1 00:00:00 1970
From: elezegarcia@gmail.com (=?ISO-8859-1?Q?Ezequiel_Garc=EDa?=)
Date: Sat, 25 Feb 2012 19:09:49 -0300
Subject: [question] between probe() and open()
Message-ID: <CALF0-+W7epb+-qFq_OLX0BoMTjszZ81-owo8HT4wr2-emqgNwQ@mail.gmail.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

Hello,

This is a question in general about usb drivers and
in particular about easycap driver.

Is there any way a driver can be accesed
between after usb_probe() but before device open()?
I guess not, since any further operation on
the device needs a struct file pointer, i.e. a file descriptor on
the user side.

In particular:
easycap driver currently calls reset() on usb_probe(),
reset() does some hardware initialization among other stuff.
However, the reset() is called once again on open().
This seems redundant, right?

The reset() is a heavy function since it access the hardware, so
it would be benefitial to change it,
but I would like someone to ack this, since it is not so trivial.

Some measures on the device shows how heavy the reset() is:

# calling reset() on usb_probe()
time modprobe easycap

real    0m1.516s
user    0m0.000s
sys     0m0.009s

---

# not calling reset() on usb_probe()
time modprobe easycap

real    0m0.003s
user    0m0.000s
sys     0m0.002s

Thanks,
Ezequiel.